Electrothermal Modelling and Measurements of Parallel-Connected VTH Mismatched SiC MOSFETs under Inductive Load Switching

In high current applications that use several parallel-connected SiC MOSFETs (e.g., automotive traction inverters), optimal current sharing is integral to overall system reliability. Threshold voltage (VTH) variation in SiC MOSFETs is a prevalent reliability issue that can cause current mismatch in parallel-connected devices. Using experimental measurements and compact modelling, a technique has been developed for characterising the impact of VTH variation in up to 8 parallel-connected SiC MOSFETs. This model can predict the allowable VTH variation for optimal current sharing. It can also be used to evaluate the impact of other parameters, including gate driver synchronisation, on current sharing in parallel devices.